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Rear control arms for sway bar

I've been led to believe that boxes equipped with a rear sway bar, and perhaps a certain handful of cars not equipped with it (but not all of production in general) have rear lower control/trailing arms constructed of thicker steel:

Originally Posted by jaywish

The issue on the rear arms is not so much the holes. Any arm can easily be drilled for the second set of holes and the lips neatly and easily rolled. More significantly is the thickness of the metal used to construct the arms. My 89 wagon came stock with the heavy constructed arms that were not preped for a sway.
Reportedly many/most other cars came with arms that look identical but are made of a slightly thinner steel. So take a set of calipers to your existing arms and compare that to the ones in the yard. I no longer have the dimensions.

I now own two rear sway bars; one skinny one mounted to arms mounted to an axle which is sleeping at Derek's house currently, and one fat bar with no arms (but do have the hardware).

I would like to put the fat bar on my Lincoln (along with the corresponding front bar), but I am concerned about this 'different control arm construction' issue. Do we know what happens if you put a rear bar, particularly the fat one, on the skinny arms? Are they just a little more flexxy or do they actually fail from fatigue?

Worth noting I have not verified it has the skinny arms, just assuming it does. I can't find measurements to confirm what is what.

Been running the fat one on the 88 for about a decade of daily use without issues on whatever crusty rusty trailing arms. I doubt we’d see any kind of failure.

Also not sure of the gauge metal on the HD arms. Need someone with a clean PI car to measure. I can measure the cleaner/no rust arms on the 90 wagon tomorrow if no one has a measurement on standard ones.

I have the HD police control arms, but never installed them on the ‘87. The factory arms on it had the two holes, so I just rolled the edge slightly and bolted it in place. No issues with the install and the body roll was significantly reduced.

As long as folks have bolted the bars to the stock non-HD arms and did not experience a critical failure as a result in the couple years following, that's good enough for me.

I want to clean up or paint or something these bars but I also want to feel exactly how much of a difference they'll make, and it's not particularly hard to put them on or take them off, so I'll go for it I guess.

When you say 'rolled the edge' I imagine we're talking about where the edge of the arm is bent out at 90 degrees from the vertical wall of the arm, and just further curling that up?

When you say 'rolled the edge' I imagine we're talking about where the edge of the arm is bent out at 90 degrees from the vertical wall of the arm, and just further curling that up?

Terrible picture since the bar wasn't the focal point here:

It's the rolled edge at the bottom. I took some vice grips and just bent it down ever so slightly until the bar set into the grove nicely and lined up properly with the holes. The HD arms are flat in those areas.

I definitely noticed a difference the the sway bar. The rear end used to have a little bit of a wandering sensation on rough roads and on tight turns. Ride quality was not impacted with the addition, but it did help keep the car more level during turns by reducing overall body roll. If you prefer the "can it lean enough to one side it might fall off the springs?" turning feel, YMMV.

"The rear control arms I have on my 89 Grand Marquis are .08 thick (left pic), and the ones I bought today are .10 thick (right pic). So the police rear control arms are made out of 12 gauge steel and the non-police rear control arms are made out of 14 gauge steel if the chart I googled is right.

Thank you. Somehow that doesn't surprise me, but it irritates me that Google could not seem to come to the same conclusion through its indexing against my search queries (as a general rule, when I say I've searched for something, I Googled my query with site:grandmarq.net at the end).

I do like body roll but this car has a lot of it. Too much, by reasonable standards.

Frankly i've been wondering if a cobra IRS would fit in the back of our cars. Only downside then is that the front suspension would be archaic in comparison. Sure would make these turds handle better though.

Yeah, there's a world of difference with the rear swaybar. Go over bumps, or railroad tracks, feel how the car WIGGLES? There's a shimmy in the rear if you don't have the control arms linked with that bar. It's a solid feeling now going over any road imperfections and it makes turning somewhat tighter (maybe not objectively) and more fun.

Hey im new here but want to put a set of bars on the front and rear of my 89 marquis from a police car. Does it matter what year car they come from and can i re use my from end links? And does the rear install right to the lower control arms or are there end links also?

79-91 should work for you up front and in the rear. Rear is control arm mount. You can reuse your end links and just replace the bushings. The energy suspension bushing kit is $20 at most local parts stores that carry them. It's not specific to these cars, but they work fine.

BTW my X 89 wagon came with the heavy gauge steel control arms but no sway. The bars were not rolled nor did they have the second set of holes to mount the bar. So I don't know if only wagons got the heavy bars or any later box. The only way I could tell the difference between the (early?) thin bars and these was with a gauge.

It was an easy conversion. Just roll the lower lip a bit, mount up the bar to the single set of holes, drill the second set of holes using the bar ass a template.